The invention relates to a process for extending petroleum derived products intended for use as a combustion fuel or as a feed stock for a refinery or coke production operation. It particularly relates to the formation of colloidal suspensions of coal particles within heavy, high boiling point petroleum fractions.
Colloidal fuels have been contemplated for use in steam engines for marine propulsion and for power boilers providing steam for utilities. Such fuels also may have applications in gas turbines or in land powered vehicles.
Coal and oil mixtures as slurries or dispersions have been regarded as a pumpable fuel that can be provided at economically attractive prices when the cost of petroleum is substantially more than that of coal. These mixtures have been prepared by grinding coal and mixing it into oil or other organic solvents to provide a fuel. To provide colloidal mixtures, the coal was ground to extremely small particle size, either separately or in mixture with the solvent. As expected, grinding costs increase with decreased particle size. Expensive wetting or stabilizing agents such as mixtures of alkylstyrene polymers, for instance as described in U.S. Pat. No. 4,130,400, have been proposed to maintain the solids suspended within the liquid. Unfortunately, without continued mixing or the use of such stabilizers, the solid coal particles often settle during storage causing difficulties in the ultimate use of the fuel mixture. Moreover, coal and oil mixtures of this kind often include ash and sulfur that may make additional processing necessary either before or after combustion.
In another area of technology, coal is liquefied by contact with hydrogen at elevated temperatures for an extended period of time to fracture and dissolve the coal into the solvent solution. Most often recycled coal liquid is used as solvent with large hydrogen and heat input rates required to hydrogenate and dissolve the large molecules of condensed aromatic ring structure of the coal. Such processes for solvating or liquefying coal are quite expensive as it is the object of these processes to reduce the coal structure to molecular size that is in liquid state at process operating temperatures. Most often, such processes liquefy substantially all of the carbonaceous material leaving only insoluble constitutents such as fusain, coke and mineral ash which is separated by sedimentation or filtration. This conversion of substantially all the carbonaceous coal material to a molecular liquid state is expensive due to the large input of heat and hydrogen for liquefying the condensed aromatic rings.
Therefore, it is an object of the present invention to provide a method of producing a coal-oil mixture that can be used as a liquid combustible fuel.
It is also an object of the invention to provide a method of preparing a colloidal dispersion of coal particles in a petroleum derived liquid.
It is a further object to provide a method of extending a liquid petroleum fuel through the addition of a solid coal material.